Rain Sensor Impedance Detection for Wiper Control
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Solution Overview
Problem
Conventional windshield wiper speed control systems are inefficient due to limited speed steps and interference from ambient light, leading to incomplete rain sensing and increased product complexity and cost.
Innovation Solution
A wiper driving apparatus featuring a substrate with sensing electrodes and a reaction layer that detects rainfall through impedance changes, using a carbon micro-coil device to determine rainfall presence and amount, and adjusts wiper operation accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light source and light receiving element are arranged with the circuit board inclined with respect to the windshield surface, then rain sensing efficiency is improved by receiving only optical signals reflected from raindrops, but interference light from the light source directly reaching the light receiving element reduces detection accuracy
Solution Approach 1:
The patent extracts and removes the harmful interference light component from the detection system. By using a time-of-flight measurement method, the system separates the useful reflected light from raindrops (which takes a specific time to return) from the interference light that reaches the sensor directly or through short-path reflections, effectively filtering out the harmful component based on temporal separation.
Solution Approach 2:
The patent introduces a time-of-flight measurement mechanism as an intermediary to distinguish between useful and harmful light signals. This intermediary method measures the time taken for light to travel to and from raindrops, creating a temporal filter that separates the detection of raindrop reflections from direct interference light reaching the sensor.
2Measurement precision
If the circuit board is inclined to minimize ambient interference light from headlights, then rain sensing accuracy is improved, but the structure becomes more complicated and productivity decreases
Solution Approach 1:
The patent makes the circuit board serve multiple functions: it provides the mounting surface for the light source and light receiving element, establishes the inclined angle for optimal raindrop reflection detection, and simultaneously acts as a reference plane for the time-of-flight measurement system. This multi-functionality eliminates the need for separate structural components to achieve the inclined positioning.
Solution Approach 2:
The circuit board performs self-positioning and self-alignment functions through its inherent structural design. The board's inclination angle is built into the mounting structure, allowing the light source and receiver to automatically achieve the correct geometric relationship with the windshield surface without requiring additional adjustment mechanisms or complex alignment procedures.
3Measurement precision
If a light source and light receiving element are arranged to detect irregular reflection signals from raindrops, then rain detection capability is improved, but light from the source spreads over a range of angles and directly reaches the receiver, lowering detection efficiency
Solution Approach 1:
The patent employs continuous pulsed light emission with time-of-flight measurement to maintain continuous detection capability. By sending out light pulses in rapid succession and measuring the return time of each pulse, the system maintains continuous monitoring of raindrops while using only the minimal necessary light energy for each measurement cycle, reducing overall energy loss.
Solution Approach 2:
The patent changes the temporal parameter of light emission from continuous to pulsed, and uses the time-of-flight parameter to distinguish useful signals from interference. This parameter change allows the system to use lower light intensities in pulses rather than continuous high-intensity light, reducing energy loss while maintaining detection efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves driver convenience by accurately responding to rainfall with adjustable wiper speed, offering enhanced precision, power efficiency, and miniaturization compared to optical systems.
Implementation Method 1
the reaction layer causes a change in an imaginary part of a positive of impedance due to a force applied by the occurrence of the rainfall and a change in a negative imaginary part of impedance due to a change in a dielectric constant caused by an object existing on the second surface
Implementation Method 2
a change in a negative imaginary part of impedance due to a change in a dielectric constant caused by an object existing on the second surface
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4
AI summary
A rain sensor according to an embodiment comprises: a substrate; a sensing electrode formed on a first surface of the substrate; a reaction layer formed on the first surface of the substrate and burying an upper surface of the substrate and the sensing electrode; a driving unit electrically connected to the sensing electrode formed on the first surface of the substrate and processing a sensing signal transmitted through the sensing electrode; and a protective layer formed surrounding the driving unit, wherein an impedance value according to a change of at least one of a force and a dielectric constant caused by presence of rainfall is changed, and the sensing electrode transmits the sensing signal with respect to a variation amount of the impedance value of the reaction layer to the driving unit.